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Biomining using microalgae has emerged as a sustainable option to extract rare earth elements (REEs). This study aims to (i) explore the capability of REEs recovery from bauxite by microalgae, (ii) assess the change of biochemical function affected by bauxite, and (iii) investigate the effects of operating conditions (i.e., aeration rate, pH, hydraulic retention time) to REEs recovery. The results showed that increasing bauxite in microalgae culture increases REEs recovery in biomass and production of biochemical compounds (e.g., pigments and Ca-Mg ATPase enzyme) up to 10 %. The optimum pulp ratio of bauxite in the microalgae culture ranges from 0.2 % to 0.6 %. Chlorella vulgaris was the most promising, with two times higher in REEs recovery in biomass than the other species. REEs accumulated in microalgae biomass decreased with increasing pH in the culture. This study establishes a platform to make the scaling up of REEs biomining by microalgae plausible.

Photocatalytic self-cleansing ZnO membranes were developed and used for pre-concentrating microalgae solution prior to harvesting. The inorganic membranes were fabricated via two different methods: (i) direct deposition of ZnO onto a porous stainless steel substrate and (ii) post-growth oxidation of a deposited metallic Zn layer. Systematic surface characterisation revealed a thin layer of homogeneous, crystalline ZnO on the porous membrane. Direct ZnO deposition resulted in a thicker layer with higher UV light absorption capability compared with the post-growth oxidization method. The ZnO coating made the membrane surface highly hydrophilic, resulting in two-fold increase in water permeance compared to the base stainless steel substrate. The high hydrophilicity of the ZnO-coated membrane also led to an increase in the permeate flux of the microalgae solution by up to 100%, making it suitable for microalgae pre-concentration. Upon UV light irradiation, the ZnO membrane demonstrated self-cleansing capability due to the photocatalytic activity of the ZnO coating layer. After 30 min of UV irradiation, the ZnO membrane could achieve 60% permeance recovery after complete fouling. No recovery was observed with the base stainless steel membrane, which was used as the control.

Atmospheric water harvesting (AWH) is considered one of the promising technologies to alleviate the uneven-distribution of water resources and water scarcity in arid regions of the world. Hydrogel-based AWH materials are currently attracting increasing attention due to their low cost, high energy efficiency and simple preparation. However, there is a knowledge gap in the screening of hydrogel-based AWH materials in terms of structure-property relationships, which may increase the cost of trial and error in research and fabrication. In this study, we synthesised a variety of hydrogel-based AWH materials, characterized their physochemcial properties visualized the electrostatic potential of polymer chains, and ultimately established the structure-property-application relationships of polymeric AWH materials. Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) hydrogel is able to achieve an excellent water adsorption capacity of 0.62 g g-1 and a high water desorption efficiency of more than 90 % in relatively low-moderate humidity environments, which is regarded as one of the polymer materials with potential for future AWH applications.

This study reports a facile technique to synthesize and tune the cationic polymer, poly(3-acrylamidopropyl)trimethylammonium chloride (PAPTAC), in terms of molecular weight and surface change for harvesting three microalgae species (Scenedesmus sp., P.purpureum, and C. vulgaris). The PAPTAC polymer was synthesised by UV-induced free-radical polymerisation. Polymer tuning was demonstrated by regulating the monomer concentration (60 to 360 mg/mL) and UV power (36 and 60 W) for polymerisation. The obtained PAPTAC polymer was evaluated for harvesting three different microalgae species and compared to a commercially available polymer. The highest flocculation efficiency for Scenedesmus sp. and P. purpureum was observed at a dosage of 25 mg-polymer/g of dry biomass by using PAPTAC-90, resulting in higher flocculation efficiency than the commercial polymer. Results in this study show evidence of effective neutralisation of the negative charge surface of microalgae cells by the produced cationic PAPTAC polymer and polymer bridging for effective flocculation. The obtained PAPTAC polymer was less effective for harvesting C. vulgaris, possibly due to other factors such as cell morphology and composition of extracellular polymeric substances of at the cell membrane that may also influence harvesting performance.

Increasing demand for thermal comfort in buildings together with the urgent need for reducing greenhouse gas emissions has resulted in significant technological advancement in the air-conditioning industry, most notably including the development of the liquid desiccant air-conditioning (LDAC) process. This innovative process involves two stages, namely air dehumidification and liquid desiccant solution regeneration, and its dehumidification capacity is regulated by the efficiency of liquid desiccant solution regeneration. Membrane distillation (MD) has been increasingly explored for regeneration of liquid desiccant solutions in LDAC systems owing to its notable advantages including excellent membrane rejection, resilience to hypersalinity, and effective incorporation of low-grade waste heat and solar thermal energy. Despite these advantages, MD regeneration of liquid desiccant solutions has been demonstrated only at the lab-scale level using direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD) configurations for manifestation of their technical feasibility. Although these lab-scale demonstrations have arguably paved the way for progress on the MD regeneration of liquid desiccant solutions, more studies at the pilot or large-scale level are required to realize this MD strategic application.

This study reports a biocatalytic system of immobilized laccase and 3D printed open-structure biopolymer scaffoldings. The scaffoldings were computer-designed and 3D printed using polylactide (PLA) filament. The immobilization of laccase onto the 3D printed PLA scaffolds were optimized with regard to pH, enzyme concentration, and immobilization time. Laccase immobilization resulted in a small reduction in reactivity (in terms of Michaelis constant and maximum reaction rate) but led to significant improvement in chemical and thermal stability. After 20 days of storage, the immobilized and free laccase showed 80% and 35% retention of the initial enzymatic activity, respectively. The immobilized laccase on 3D printed PLA scaffolds achieved 10% improvement in the removal of estrogens from real wastewater as compared to free laccase and showed the significant reusability potential. Results here are promising but also highlight the need for further study to improve enzymatic activity and reusability.

This study investigated the impact of hydraulic retention time (HRT) on the removal of veterinary antibiotics by an anaerobic membrane bioreactor (AnMBR) for swine wastewater treatment. Ten commonly used antibiotics in the group of tetracyclines, fluoroquinolones, and sulfonamides were evaluated. Results show that a wide variation from 21 to 99% was observed for antibiotic removal by AnMBR regardless of the applied HRT. The methane yield increased from 0.22 L/g COD to 0.28 L/g COD as the operational HRT was prolonged from 24 to 48 h for AnMBR. Doubling the HRT value enhanced removal of most antibiotics and methane yield by 2–30% and 22–47%, respectively. The enhanced antibiotic removal in response to HRT prolongation could be positively correlated to the enrichment of the genus unidentified_Synergistaceae. Moreover, prolonging HRT increased the relative abundance of the genera unidentified_Synergistaceae, Geobacter and Methanobrevibacter, which could strengthen hydrogenotrophic methanogenesis to enhance methane yield. In addition, HRT increase reduced the ratio of protein to polysaccharide in both extracellular polymeric substances and soluble microbial products, thereby, alleviating membrane fouling in AnMBR operation.

This study demonstrates the complementarity between alkaline-thermal treatment and zero-valent iron immobilized in biochar (BC-ZVI) for enhanced degradation of perfluorooctanoic acid (PFOA). New and complementary research techniques, including 19F-NMR and density functional theory (DFT) analysis were used to evaluate defluorination efficiency and elucidate possible degradation mechanisms. The defluorination of PFOA was governed primarily by alkaline strength while BC-ZVI could enhance reaction kinetics by 2.4 times. Adsorption of the intermediates to BC-ZVI resulted in near-complete removal of all fluorinated compounds (with the exception of perfluoracetic acid) in the aqueous phase within 15 min of reaction. After 4 h of alkaline hydrothermal treatment (240 °C and 250 mM NaOH) with BC-ZVI, defluorination efficiency of PFOA of 99.7% was observed. Perfluoracetic acid was the only persistent byproduct but accounted only for less than 1% of the initial PFOA. DFT analysis also showed that strong alkaline conditions could decrease the reaction energy barrier by 73.9% due to the decarboxylation of PFOA via nucleophilic substitution. In addition to Kolbe decarboxylation, the profile of intermediate products and DFT analysis results suggest that PFOA was degraded by other mechanisms leading to near-complete and effective defluorination.

The membrane bioreactor (MBR) process is a ground-breaking innovation in the field of wastewater treatment, which involves a biological activated sludge process coupled with the membrane separation. The main highlights of the MBR are its low footprint, which is due to the elimination of secondary sedimentation process in the conventional activated sludge (CAS). MBR can produce high and consistent effluent quality, which can be a non-potable water source or be readily treated in downstream processes for potable water reuse. With the decrease in the cost of membrane modules over the years, full-scale deployment of MBR plants continues to increase worldwide with scale up to 800 MGD to date. Nevertheless, membrane fouling and energy consumption in MBRs are two technical challenges. MBR membranes are prone to fouling by organic matter originating from the microbial cells. Energy consumption in MBRs is higher than the CAS due to the aeration requirements, particularly for membrane scouring. Several mitigations strategies to address these challenges have been developed, which showed promising results by reducing the operating cost of the MBR plants. These strategies include the development of new membrane materials with chemical and biological resistant properties, novel configurations for enhanced process performance as well as fouling mitigation and control. This chapter aims to present a succinct overview of the status of MBR technology for municipal and industrial wastewater treatment to cover the recent development of energy reduction and fouling mitigation. It is envisioned that MBR will continue as a domain technology in wastewater treatment sector.

Increased rainfall intensity due to climate change is expected to exacerbate flood inundation in urban areas. Water sensitive urban design (WSUD) provides a variety of benefits in stormwater quantity management, ranging from stormwater harvesting to flood mitigation. Currently, however, developed areas lack any system that can improve the management of existing stormwater harvesting facilities to increase stormwater storage capacity without enlarging the stormwater drainage system. This study modelled a new method, Site Real-Time Adaptive Control (SRAC), that combined existing stormwater harvesting infrastructure at both regional and site levels with the existing stormwater drainage system (SWDS) through a cloud computing platform to increase stormwater storage capacity and reduce runoff water to the surface. The research found that: (1) the SRAC can manage runoff water dynamically and reduce flood inundation. The proposed impact factor Mt could help designers to measure the recovery capacity between two continuous rainfall events; (2) the SRAC model could postpone the peak flow in the trunk drainage system by 8–10 min; (3) the SRAC model could remove most of the excess water during very frequent rainfall events, decreasing over 98 % excess flow in design events 1h1EY (14,650 m3) and 2h1EY (11,272 m3); (4) the SRAC model showed a 36–50 % reduction in total outfall volume in the 1 h rainfall events, a 42–50 % reduction in the 2 h rainfall events; (5) the SRAC model could increase the capacity of downstream water treatment plants and save 43 % of the stormwater trunk drainage demand.

Population growth rapidly increased waste activated sludge (WAS) production in wastewater treatment plants (WWTPs), making the expansion of sludge treatment capacity urgent. Free ammonia (FA) pretreatment is experimentally applied to expand the treatment capacity of an anaerobic digester through reducing sludge retention time (SRT) for the first time. Two semi-continuous flow mesophilic (37 °C) anaerobic digestion systems, control system with a uniform SRT of 12 d and the experimental systems with progressively reduced SRTs (from 12 d to 10 d and then 8 d), were operated for>7 months. The volatile solids (VS) destruction in the experimental system at a SRT of 8 d was comparable to the control system (30.0 ± 1.4 % vs 30.5 ± 1.7 %) but increased by 16.2 % (35.1 ± 1.5 % vs 30.2 ± 1.4 %) under an SRT of 10 d, which was supported by methane production and total chemical oxygen demand (COD) removal. The biomass-specific hydrolysis rate was significantly increased by up to 80 % (from 0.05 ± 0.01 g COD/g VS/d to 0.09 ± 0.01 g COD/g VS/d), which may contribute to the expanded capacity. The volatile fatty acids (VFAs)/alkalinity of systems maintained a reasonable range (0.01 – 0.06), suggesting the stability of digesters. FA pretreatment played a dominant role in the changes in the bacterial microbial community (52.80 % in PC1) and archaeal community (94.25 % in PC1). FA pretreatment improved the removal of pathogen by 1.3–2.0 log and antibiotic resistance genes by 34–86 %. This study first demonstrated that FA pretreatment expands the treatment capacity of an anaerobic digester by up to 50 % with economic and environmental benefits, promoting FA pretreatment to be a wider and pragmatic implementation for WWTPs.

Primary sludge (PS) is one of the major sludge sources for anaerobic digesters in wastewater treatment plants. Although the impact of free ammonia (FA) pretreatment on methane production from anaerobic PS digestion was previously investigated using batch biochemical methane potential tests, these tests could not fully represent the continuous/semi-continuous anaerobic digestion that is currently used in practice. This study comprehensively evaluated the impact of FA pretreatment on the performance of anaerobic PS digestion for the first time using semi-continuous systems that run for over 120 days. FA pretreatment (560 mg NH3-N/L, 24 h) improved the volatile solids (VS) removal of PS by 12.2 % from 60.5 % to 67.9 %, with a similar improvement in total chemical oxygen demand removal of 14.9 % and methane production of 16.1 %. FA pretreatment increased the biomass-specific hydrolysis rate of digesters by 23.5 %. Model-based analysis revealed that the enhanced anaerobic digestion performance may be due to both the increased apparent hydrolysis rate (increased by 26.7 %) and the enhanced degradability extent (increased by 9.5 %) of PS, caused by FA pretreatment. The dewaterability of digested sludge was enhanced by 14.0 % due to FA pretreatment, which is also supported by the reduced capillary suction time from 15.1 s to 10.9 s. Removals of Fecal Coliform and E. Coli were enhanced by 0.6 and 1.4 log Most Probable Number/g vS by FA pretreatment. This study firstly manifested that FA pretreatment is a favourable approach to improve the performance of anaerobic PS digestion with extra benefits in pathogen removal and dewaterability.

Co-culture of microalgae-activated sludge has the potential to purify wastewater while reduce energy demand from aeration. In this work, a mechanically stirred membrane photobioreactor (stirred-MPBR) was used to evaluate the impact of the biomass retention time (BRT) on the treatment performance and membrane fouling. Results showed that stirred-MPBR was affected by BRT during treating domestic wastewater at a flux of 16.5 L m-2 h-1. The highest productivity was attained at BRT 7d (102 mg L-1 d-1), followed by BRT 10d (86 mg L-1 d-1), BRT 5d (85 mg L-1 d-1), and BRT 3d (83 mg L-1 d-1). Statistical analysis results showed that BRT 7d had a higher COD removal rate than BRT 10d, however, there is no difference in total nitrogen removal rate. The highest TP removal occurred when the biomass operated at BRT as short as 3d. Reduced BRTs caused a change in the microalgae-activated sludge biomass fraction that encouraged nitrification activity while simultaneously contributing to a higher fouling rate. The bound protein concentrations dropped from 31.35 mg L-1 (BRT 10d) to 10.67 mg L-1 (BRT 3d), while soluble polysaccharides increased from 0.99 to 1.82 mg L-1, respectively. The concentrations of extracellular polymeric substance fractions were significantly altered, which decreased the mean floc size and contributed to the escalating fouling propensity. At the optimum BRT of 7d, the stirred-MPBR showed sufficient access to light and nutrients exchange for mutualistic interactions between the microalgae and activated sludge.

Harvesting and water reuse are two critical issues for large-scale microalgae cultivation. Using two representative microalgae species, namely C. vulgaris and Scenedesmus sp., this study evaluates the performance of a ceramic microfiltration membrane to extract clean water for reuse and pre-concentrate the microalgae solution for subsequent harvesting. The results show that fouling was specific to each individual microalgae species due to the difference in cell properties (e.g. size, shape, and cell membrane). Importantly, membrane fouling could be efficiently mitigated by aeration and regular backwashing without any chemical addition. Aeration reduced the transmembrane pressure when filtering C. vulgaris and Scenedesmus sp. by 56 and 38%, respectively. In long-term performance experiments, C. vulgaris showed considerable membrane fouling over time; by contrast, Scenedesmus sp. showed negligible fouling. The results reaffirmed that membrane filtration efficiency was microalgae species-specific. Permeate water reuse for growing another batch of microalgae was also demonstrated using both species. Results reported here suggest that ceramic microfiltration membrane can simultaneously enrich the microalgae solution and recycle permeated water for microalgae cultivation.

Nitrofurans are broad-spectrum bactericidal agents used in a large quantity for veterinary and human therapy. This study reports the long-term impact of two nitrofuran representatives, nitrofurantoin (NFT) and furaltadone (FTD) on the bacterial strains Sphingobacterium siyangense FTD2, Achromobacter pulmonis NFZ2, and Stenotrophomonas maltophilia FZD2, isolated from a full-scale wastewater treatment plant. Bacterial whole genome sequencing was used for preliminary strains characterization. The metabolomic, electrochemical, and culture methods were applied to understand changes in the bacterial strains after 12-month exposure to nitrofurans. The most significantly altered metabolic pathways were observed in amino acid and sugar metabolism, and aminoacyl-tRNA biosynthesis. Disrupted protein biosynthesis was measured in all strains treated with antibiotics. Prolonged exposure to NFT and FTD also triggered mutagenic effects, affected metabolic activity, and facilitated oxidative stress within the cells. Nitrofuran-induced oxidative stress was evidenced from an elevated activity of catalase and glutathione S-transferases. NFT and FTD elicited similar but not identical responses in all analyzed strains. The results obtained in this study provide new insights into the potential risks of the prolonged presence of antimicrobial compounds in the environment and contribute to a better understanding of the possible impacts of nitrofuran antibiotics on the bacterial cells.

This work describes the design and fabrication of zirconia-fucoidan (ZrF) using the modified sol–gel method as the substrate for laccase immobilization (ZrF-laccase). Based on Bradford analysis, the amount of immobilized laccase and the immobilization efficiency were determined at 130 mglaccase/gsupport and 87%, respectively. The immobilization efficiency was also confirmed by determining physicochemical parameters (such as spectroscopic, thermal stability, electrokinetic, surface area and pore volume) of the prepared zirconia-fucoidan materials with and without laccase immobilization. The decrease in the value of the isoelectric point (from 6.4 to 4.0), the specific surface area (from 366 to 108 m2/g) and the pore volume (from 0.33 to 0.18 mL/g) after the immobilization process indicates effective immobilization of the laccase on the zirconia-fucoidan material. The relative activity of immobilized laccase was determined using the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) oxidation reaction. The ZrF-laccase biocatalytic system exhibits higher enzymatic activity than free laccase under a range of pH and temperature conditions (above 40% of initial activity) and can be reused in ten reaction cycles, retaining approximately 80% of its initial activity. The ZrF-laccase biocatalytic system was evaluated for the degradation of tartrazine as a model azo dye. The ZrF-laccase biocatalytic system could achieve 95% tartrazine decolorization in five repetitive cycles. Based on mass spectroscopy analysis, the pathway of tartrazine degradation was also proposed. Proposed methodology as well combination of zirconia, fucoidan and laccase appear to be a promising approach and open new pathways for production of highly effective biocatalyst for various applications focused on removal of emerging pollutants from the environment.

This study investigated the impacts of different coagulants on the performance of membrane distillation (MD) for landfill leachate concentrate treatment. Three common coagulants, including polyaluminum chloride (PAC), polyferric sulfate (PFS), and ferric chloride (FeCl3), were compared at different dosages. MD performance was then evaluated regarding both contaminant retention and membrane fouling in the treatment of coagulated leachate concentrate. Results show that the three coagulants exhibited desirable performance for floc formation and thus the removal of organic matter, mainly humic substances (>80% as indicated by total organic carbon), at a dosage of 1200 mg L−1. As such, coagulation enhanced the MD performance for contaminant removal and fouling mitigation with the highest increase in ammonium retention from 48.3% to 90.1%. Of the three coagulants, PFS was the most effective for improving MD capability for the retention of heavy metals and volatile organic compounds. Furthermore, PFS could synergistically remove organic and inorganic foulants (e.g. humic acid, and calcium and magnesium ions) in the coagulation of landfill leachate concentrate to alleviate membrane fouling in subsequent MD operation.

A series of C-doped Bi3O4X (X = Cl, Br, I) photocatalysts with layer-stacked structure was synthesized using glucose as carbon source, and the carbon doping and halogen species on harvesting broader solar spectrum and promoting charge carrier separation were systematically investigated. For pyrene photolysis, the photodegradation rate of pristine materials followed the order of Bi3O4I > Bi3O4Br > Bi3O4Cl, which was attributed to the difference in electronegativity of the halogen elements. The doped carbon boosted photocatalytic performance and the optimal C/Bi3O4I achieved 100% pyrene removal within 20 min, which primarily benefited from the dramatic improvement of the internal electric field (IEF). The improved IEF further increased the separation and transfer efficiency of photogenerated charge carriers. XRD and XPS characterizations confirmed that the doped carbon implanted into the lattice of [X] layers, and mainly affected the X np states. The X np orbitals contributed to the valence band (VB) of Bi3O4X, thus the local occupied states induced by doped carbon formed above VB and significantly decreased the VB potential. Meanwhile, the doped carbon narrowed the band gap and greatly improved visible light utilization. The [rad]O2−, h+ and [rad]OH were identified as dominant active species for pyrene degradation, and the generation rate of [rad]O2− and [rad]OH was further measured by the probe technique. Moreover, the photodegradation pathways of pyrene were proposed and the ecotoxicity of intermediates was assessed. This study reveals the effect of halogen species on photocatalytic activity and provides guidance for enhancing IEF by doping inorganic element.

This study mapped the fate of antibiotics in a swine farm with integrated waste treatment including anoxic stabilization, fixed-film anaerobic digestion, anoxic-oxic (A/O), and composting. Results show the prevalent and consistent occurrence of 12 antibiotics in swine waste. Mass balance of these antibiotics was calculated to track their flow and evaluate their removal by different treatment units. The integrated treatment train could effectively reduce antibiotic loading to the environment by 90% (measured as combined mass of all antibiotic residues). Within the treatment train, anoxic stabilization as the initial treatment step, accounted for the highest contribution (43%) to overall antibiotic elimination. Results also show that aerobic was more effective than anaerobic regarding antibiotic degradation. Composting accounted for an additional of 31% removal of antibiotics while anaerobic digestion contributed to 15%. After treatment, antibiotic residues in the treated effluent and composted materials were 2 and 8% of the initial antibiotic loading in raw swine waste, respectively. Ecological risk assessment showed negligible or low risk quotient associated with most individual antibiotics released into the aquatic environment or soil from swine farming. Nevertheless, antibiotic residues in treated water and composted materials together showed significant ecological risk to water and soil organisms. Thus, further work to improve treatment performance or develop new technologies is necessary to reduce the impact of antibiotics from swine farming.

This review aims to summarise the current state of the art technologies for phosphorus recovery from waste and wastewater. Information corroborated here shows a clear relationship between PO4-P content in the liquid phase and the cost of phosphorus recovery. In fact, all current commercial scale operations in this review involve a phosphorus-rich waste stream. In most cases, phosphorus recovery is achieved via two key steps: solubilising phosphorus into water and then phosphate recovery via chemical precipitation/crystallisation. Recent development has also included enrichment and pre-treatment of the phosphorus rich liquid stream. Phosphorus is also a contaminant in the aquatic environment. Thus, this work also reviews the post-treatment of the liquid stream after phosphorus recovery for environmental discharge or water reuse. This review places a spotlight on the requirement for further research work especially on phosphorus enrichment at pilot- and full-scale level. The review also demonstrates the need for further research on pre-treatment and post-treatment to complement the recovery process via chemical precipitation.

The surface reactivity of biochar derived from waste biomass has not been well understood due to its complex composition and heterogeneity. Therefore, this study synthesized a series of biochar-like hyper-crosslinked polymers (HCPs) with different amounts of phenolic hydroxyl groups on the surface as an indicative tool to investigate the roles of key surface properties of biochar on transforming pollutants being adsorbed. Characterization of HCPs suggested that electron donating capacity (EDC) of different HCPs was positively correlated with increasing amounts of phenol hydroxyl groups, whereas specific surface area, degree of aromatization and graphitization were negatively correlated. It was found that greater amounts of hydroxyl radicals were produced with increasing amounts of hydroxyl groups on the synthesized HCPs. Batch degradation experiments with trichlorophenols (TCPs) suggested that all HCPs could decompose TCP molecules upon contact. The degree of TCP degradation (~45 %) was highest for HCP made from benzene monomer with the lowest amounts of hydroxyl groups, which was likely driven by its greater specific surface area and reactive sites for TCP degradation. Conversely, the degree of TCP degradation (~25 %) by HCPs with the highest hydroxyl group abundance was the lowest, probably because the lower surface area of HCPs had limited TCP adsorption, which led to lower interaction between HCP surface and TCP molecules. The results concluded from the contact of HCPs and TCP suggested both EDC and adsorption capacity of biochar played critical roles in transforming organic pollutants.

This study aims to reveal the underlying mechanisms of mature compost addition for improving organic waste composting. Composting experiments and metagenomic analysis were conducted to elucidate the role of mature compost addition to regulate microbial metabolisms and physiological behaviors for composting amelioration. Mature compost with or without inactivation pretreatment was added to the composting of kitchen and garden wastes at 0%, 5%, 10%, 15%, and 20% (by wet weight) for comparison. Results show that mature compost promoted pyruvate metabolism, tricarboxylic acid (TCA) cycle, and oxidative phosphorylation to produce heat and energy to accelerate temperature increase for composting initiation and biological contaminant removal (>78%) for pasteurization. Energy requirement drives bacterial chemotactic motility towards nutrient-rich regions to sustain organic biodegradation. Nevertheless, when NADH formation exceeded NAD+ regeneration in oxidative phosphorylation, TCA cycle was restrained to limit continuous temperature increase and recover high intracellular NAD+/NADH ratio to secure stable oxidation reactions.

This study investigated the performance of lignocellulosic wastes to regulate microbial interactions to improve the composting of digestate from the anaerobic digestion of food waste regarding organic mineralization and humification. Garden waste, rice husk, and cornstalks with diverse lignocellulosic biomass compositions and structures were representatively selected for comparison. High-throughput sequencing was integrated with a modular network analysis to decipher microbial community structures and their interactions. Results showed that mixing 15% of cornstalks and garden waste with digestate (wet weight) was more effective than rice husk to enrich functional microbes (e.g., Tepidimicrobium and Mortierella) to promote the microbial interkingdom for lignocellulosic degradation and humus formation. In particular, a stronger bacterial intrakingdom mutualism was observed with cornstalk addition to facilitate the progressive succession of bacteria in digestate from anaerobic to aerobic and thus inhibit the activities of anaerobic and denitrifying microbes to reduce the emissions of methane and nitrous oxide by 14.2-49.1%. Furthermore, garden waste with more lignin could effectively strengthen intrakingdom mutualism within fungi and their interkingdom interaction with bacteria to mitigate organic carbon mineralization and reduce carbon dioxide emission by 39.8-42.7%. By contrast, rice husk weakened microbial interkingdom mutualisms to retard organic biodegradation and humification during digestate composting. Results from this study provided fundamental understanding on selecting lignocellulosic wastes to regulate organic biotransformation and to improve humification and simultaneously mitigate gaseous emissions in digestate composting.

This study demonstrated the importance of fermentation broth pretreatment and dewatering by forward osmosis (FO) before keto carboxylic acid recovery. The most effective and profitable pretreatment procedure was a combination of centrifugation, ceramic ultrafiltration of molecular weight cut-off of 15 kDa, and ceramic nanofiltration of molecular weight cut-off of 450 Da. By applying the complex pretreatment and FO as a pre-concentration step of fermentation broth dewatering, the keto acid enrichment of two times was achieved for alpha-ketoglutaric acid and pyruvic acid. Extensive fouling analysis performed in this study confirmed that the proposed pretreatment procedure was sufficient to avoid severe fouling of the FO dewatering process. A techno-economic analysis of the proposed keto acid extraction scheme shown that by using FO for fermentation broth dewatering, the total capital investment was reduced and the payback time was shortened by 0.83 yr.

This study demonstrates a novel application of steel-making slag for quenching residual phosphorus in wastewater effluent after chemical precipitation. The results showed that the phosphorus removal efficiency was low without the supernatant pH adjustment. Decreased pH of the supernatant resulted in increased removal efficiency. At the optimal conditions (i.e. pH 8.5 and steel-making slag dosage of 5 g/L), approximately 98% phosphorus removal could be achieved with the output level of less than 0.1 mg/L. The results also demonstrated that enhanced phosphorus removal by pH adjustment resulted from the involvement of adsorption in the removal process. This observation was evidenced via the compliance with Langmuir isotherm of the adsorption of phosphorus to steel-making slag at decreased pH. In addition, the results indicated that the presence of inorganic carbon in the supernatant could facilitate phosphorus removal via co-precipitation effects.

This study tracked the fate of nine detected heavy metals in an industrial swine farm with integrated waste treatment, including anoxic stabilization, fixed-film anaerobic digestion, anoxic-oxic (A/O), and composting. Results show that heavy metals exhibited different transformation behaviors in the treatment streamline with Fe, Zn, Cu and Mn as the most abundant ones in raw swine waste. The overall removal of water-soluble heavy metals averaged at 30 %, 24 % and 42 % by anoxic stabilization, anaerobic digestion and A/O unit, respectively. In particular, anoxic stabilization could effectively remove Cu, Mn and Ni; while A/O unit was highly effective for Fe, Cr and Zn elimination from water-soluble states. As such, the environmental risk of liquid products for agricultural irrigation decreased gradually to the safe pollution level in swine waste treatment. Furthermore, heavy metals in the solid (slurry) phase of these bioprocesses could be immobilized with the passivation rate in the range of 42-70 %. Nevertheless, heavy metals preferably transformed from liquid to biosolids to remain their environmental risks when biosolids were used as organic fertilizer in agriculture, thereby requiring effective strategies to advance their passivation in all bioprocesses, particularly composting as the last treatment unit.

This study provided new insight to the underlying mechanisms, by which organic compositions, including protein, fat, degradable carbohydrates and lignocellulose, regulate the performance of solid-state anaerobic digestion (SSAD) for synergistic treatment of organic wastes. Results show that the feedstock with a balanced composition of protein, fat, degradable carbohydrates and lignocellulose could maintain SSAD homeostasis to enhance methane (CH4) production by 14–487%. On the other hand, organic waste with a high content of degradable carbohydrates and fat at 39 and 14%, respectively, showed an initially high CH4 production at the beginning but a lower overall CH4 production. This was because of the accumulation of volatile fatty acids (VFAs) and ammonium nitrogen (NH4+-N) at up to 17.3 and 7227.7 mg·L−1, respectively, leading to anaerobic activity inhibition. Microbial dynamic and modular network analyses indicated that the balanced feedstock secured stepwise biodegradation of different organic substances to reduce the relative abundance of hydrolytic bacteria (e.g. Rikenellaceae_RC9_gut_group and Tepidimicrobium), thus alleviating VFAs and NH4+-N stresses. In particular, fat in the balanced feedstock could not only enrich the phylum Firmicutes for macromolecular biodegradation and genes for VFAs production, but also inhibit relative oxidizers (e.g. Synergistes and Acinetobacter) to facilitate propionate and acetate production to strengthen acetotrophic methanogenesis for effective CH4 yield. Results in this study show that a balanced organic composition could regulate microbial dynamics and symbiosis to advance SSAD homeostasis and methanation in synergistic organic waste treatment.

This study demonstrated a novel technique to achieve partial nitritation/anammox (PN/A) to treat inorganic low-strength wastewater by using a 10 L continuous reactor equipped with fiber carriers. Aeration control was the key factor in single-state PN/A performance stability under oxygen-limiting conditions. Intermittent aeration was successfully adapted in this study to achieve over 80% nitrogen removal at the nitrogen loading rate of 0.12–0.16 kg N m−3 d−1. The nitrite-oxidizing bacteria activities were inhibited by intermittent aeration due to the alternate between aerobic to anoxic conditions. Ammonium-oxidizing bacteria (AOB) and anammox bacteria could be symbiotically supported within the biofilm with a specific activity of anammox bacteria that was 1.5 times higher than that of AOB. The biomass was efficiently retained by using fiber carriers. The results obtained from this study could bring the possibility of applying an energy-saving and efficient biofilm single-stage PN/A process in tropical regions.

This study examined the removal and enantio‑specific fate of a suite of eleven chiral 2-arylpropionic acids (2-APAs) during biological wastewater treatment simulated in a laboratory-scale membrane bioreactor (MBR). Using pure (R)- and (S)- enantiomers in the MBR influent, chiral inversion was determined through the increase in the concentration of the non-dominant enantiomer and changes in the enantiomeric fraction (EF) between the two enantiomers during the treatment process. Effective (>90%) and similar removal rates between (R)- and (S)- enantiomers were confirmed for eight 2-APAs. In this study, 2-APAs exhibited diverse and distinctive chiral inversion behaviours: two 2-APAs showed (R→S) unidirectional inversion, three 2-APAs showed (S→R) unidirectional inversion, and six 2-APAs showed bidirectional inversion. This is the first study to report chiral inversion behaviours of a comprehensive suite of 2-APAs with a variety of functional groups substituted onto the aryl ring. A decrease in effluent EF over time was observed for two 2-APAs. This study shows that chiral inversion of 2-APAs varies significantly from compound to compound, despite the high similarity in their chemical structures.

This work examined the chiral inversion of 2-arylpropionic acids (2-APAs) under anaerobic conditions and the associated microbial community. The anaerobic condition was simulated by two identical anaerobic digesters. Each digester was fed with the substrate containing 11 either pure (R)- or pure (S)-2-APA enantiomers. Chiral inversion was evidenced by the concentration increase of the other enantiomer in the digestate and the changes in the enantiomeric fraction between the two enantiomers. Both digesters showed similar and poor removal of 2-APAs (≤30%, except for naproxen) and diverse chiral inversion behaviors under anaerobic conditions. Four compounds exhibited (S → R) unidirectional inversion [flurbiprofen, ketoprofen, naproxen, and 2-(4-tert-butylphenyl)propionic acid], and the remaining seven compounds showed bidirectional inversion. Several aerobic and facultative anaerobic bacterial genera (Candidatus Microthrix, Rhodococcus, Mycobacterium, Gordonia, and Sphingobium) were identified in both digesters and predicted to harbor the 2-arylpropionyl-CoA epimerase (enzyme involved in chiral inversion) encoding gene. These genera presented at low abundances, <0.5% in the digester dosed with (R)-2-APAs and <0.2% in the digester dosed with (S)-2-APAs. The low abundances of these genera explain the limited extent of chiral inversion observed in this study.

Membrane-based water reuse through reverse osmosis (RO) and nanofiltration (NF) faces a critical challenge from organic micropollutants (OMPs). Conventional polyamide RO and NF membranes often lack adequate selectivity to achieve sufficient removal of toxic and harmful OMPs in water. Tailoring membrane chemistry and structure to allow highly selective removal of OMPs has risen as an important topic in membrane-based water reuse. However, a critical literature gap remains to be addressed: how to design membranes for more selective removal of OMPs. In this review, we critically analyzed the roles of membrane chemistry and structure on the removal of OMPs and highlighted opportunities and strategies toward more selective removal of OMPs in the context of water reuse. Specifically, we statistically analyzed rejection of OMPs by conventional polyamide membranes to illustrate their drawbacks on OMPs removal, followed by a discussion on the underlying fundamental mechanisms. Corresponding strategies to tailor membrane properties for improving membrane selectivity against OMPs, including surface modification, nanoarchitecture construction, and deployment of alternative membrane materials, were systematically assessed in terms of water permeance, OMPs rejection, and water-OMPs selectivity. In the end, we discussed the potential and challenges of various strategies for scale-up in real applications.

Microalgal biomass has been proved to be a sustainable source for biofuels including bio-oil, biodiesel, bioethanol, biomethane, etc. One of the collateral benefits of integrating the use of microalgal technologies in the industry is microalgae's ability to capture carbon dioxide during the application and biomass production process and consequently reducing carbon dioxide emissions. Although microalgae are a feasible source of biofuel, industrial microalgae applications face energy and cost challenges. To overcome these challenges, researchers have been interested in applying the bio-refinery approach to extract the important components encapsulated in microalgae. This review discusses the key steps of microalgae-based biorefinery including cultivation and harvesting, cell disruption, biofuel and value-added compound extraction along with the detailed technologies associated with each step of biorefinery. This review found that suitable microalgae species are selected based on their carbohydrate, lipid and protein contents and selecting the suitable species are crucial for high-quality biofuel and value-added products production. Microalgae species contain carbohydrates, proteins and lipids in the range of 8% to 69.7%, 5% to 74% and 7% to 65% respectively which proved their ability to be used as a source of value-added commodities in multiple industries including agriculture, animal husbandry, medicine, culinary, and cosmetics. This review suggests that lipid and value-added products from microalgae can be made more economically viable by integrating upstream and downstream processes. Therefore, a systematically integrated genome sequencing and process-scale engineering approach for improving the extraction of lipids and co-products is critical in the development of future microalgal biorefineries.

Improper use of conventional plastics poses challenges for sustainable energy and environmental protection. Algal derivatives have been considered as a potential renewable biomass source for bioplastic production. Algae derivatives include a multitude of valuable substances, especially starch from microalgae, short-chain length polyhydroxyalkanoates (PHAs) from cyanobacteria, polysaccharides from marine and freshwater macroalgae. The algae derivatives have the potential to be used as key ingredients for bioplastic production, such as starch and PHAs or only as an additive such as sulfated polysaccharides. The presence of distinctive functional groups in algae, such as carboxyl, hydroxyl, and sulfate, can be manipulated or tailored to provide desirable bioplastic quality, especially for food, pharmaceutical, and medical packaging. Standardizing strains, growing conditions, harvesting and extracting algae in an environmentally friendly manner would be a promising strategy for pollution control and bioplastic production.